Phenolic resins are synthetic materials that vary greatly in molecular structure. This variety allows for a multitude of applications for these resins; for example, use as a curing agent and/or to prepare the corresponding epoxy, cyanate and/or allyl thermosettable resins. These curing agents and/or resins can provide enhanced physical and/or mechanical properties to a cured composition, such as increased glass transition temperature (Tg). To achieve improved properties, however, would require the resin to have a high functionality (i.e., chemical groups available for cross linking). However, as the functionality increases in these resins, so does their molecular weight, which increases the melt viscosity of the resin and can lead to difficulties in using such resins.
One strategy for preparing thermosettable epoxy resins is to convert a phenol into a glycidyl ether. An example is the diglycidyl ether of the diphenol of cyclododecanone (eCDON), which is an epoxy resin useful in structural or electrical laminates and/or composites, functional powder coatings, etc. However, for thermosets of eCDON there is a need to 1) increase Tg, 2) increase thermal stability (for example improve maintenance of Tg with thermal cycling), and 3) improve curing profile (for example decrease onset to cure temperature and cure enthalpy). Thermosets of epoxy resins of CDD polyphenols have now surprisingly been found to provide remarkable Tg's (>300° C.) and improved cure profile including rapid onset to cure and reduced cure enthalpy. Furthermore when used in blends for example with eCDON, epoxy resins of CDD polyphenols may impart increased Tg, thermal stability and/or improved cure profile to the thermosets thereof. Thermosets with improvements in one or more of these properties find added utility in higher performance thermosets, useful in structural or electrical laminates and/or composites, multilayer electronic circuitry, integrated circuit packaging (such as “IC substrates”), filament windings, moldings, encapsulations, castings, composites for aerospace applications, adhesives, functional powder coatings and other protective coatings. In related U.S. application No. 61/602,840, filed Feb. 24, 2012, Applicants reported the preparation of the trialdehyde of cyclododecane and its subsequent conversion to polyphenols such as the hexaphenol. Applicants now report the conversion of the CDD polyphenols to the corresponding thermosettable polyglycidyl ethers (PGEs). Said PGEs may be blended with one or more other epoxy resins, such as eCDON and with one or more curing agents and/or curing catalysts to form a curable blend having increased Tg, increased thermal stability and/or improved cure profile when compared to thermosets of eCDON alone.
The high functionality of the PGEs disclosed herein provide high crosslink density upon curing. This high crosslink density translates to very high Tg temperatures, enhanced thermal stability, more rapid development of Tg during curing, and improved reactivity on curing, as demonstrated in the Examples (below).
The PGEs of the present invention are especially useful as a component in formulations with one or more conventional epoxy resins to provide improved properties. Numerous other benefits are expected from the PGEs, including very high modulus, increased moisture resistance and increased corrosion resistance.
The cured compositions described herein are particularly useful in the aerospace industry, the electronics industry (where they may be used in laminates or composites) and as a powder coating, particularly a functional powder coating as is used on pipe and rebar, where high Tg, solvent resistance, abrasion resistance and/or toughness may be beneficial. The cured compositions may be used in the form of sheets, films, fibers or other shaped articles.